RBR50 LAN Port Issues

[JohnPhotography]

I have an iMac running on High Sierra 10.13.6 that was working fine on my previous set up.

Today, I had Spectrum upgrade my cable modem to a GIG modem.

Wireless works flawlessly.  Flies!

Now I have my iMac and my PS4 hardwired initially from the cable modem.  Worked great.

Now with the new GIG cable modem, since it only has one ethernet port; I had to connect both iMac and PS4 to directly to my Orbi router.  PS4 works great hardwired, but iMac will not recognize the cable that's correctly plugged in.  I plugged the PS4 ethernet cable and it would not recognize it on the iMac.

I connected the iMac directly to the GIG cable modem and works great.  This is the only wired connection I've had success with.

I've checked all CAT7 cables and they're all brand new and confirmed to work.  I've had the same set up with my previous cable modem.

PLEASE HELP!

[FURRYe38]

What is the model# of this ISP modem?

How is the Orbi router configured? Router or AP mode?

[JohnPhotography]

Spectrum Cable Model #E31T2V1

Not sure how it's configured.  I recently factory reset it and dit not change anything.

[FURRYe38]

I think your ISP modem already has a built in router.

Modem Combo Units:
Couple of options,
1. Configure the modem for transparent bridge mode. Then use the Orbi router in router mode. You'll need to contact the ISP for help and information in regards to the modem being bridged correctly.
2. If you can't bridge the modem, disable ALL wifi radios on the modem, configure the modems DMZ for the IP address the Orbi router gets from the modem. Then you can use the Orbi router in Router mode.
3. Or disable all wifi radios on the modem and connect the Orbi router to the modem, LAN to LAN and configure AP mode on the Orbi router.

[JohnPhotography]

I called Spectrum and they said the cable modem is only a modem, not a router.

They also said that since I can plug in directly to the cable modem with the iMac and get internet access, they can't help trouble shoot the issues withi the ORBI.

Now what?

[FURRYe38]

When you connect your Mac to the Orbi, check the networking settings on the mac. Is it getting an IP address. Be sure it's set up for automatic IP addressing and not a static by chance. 

Try connecting the Mac to the Orbi wireless? 

You said "Wireless works flawlessly.  Flies" where were you connected when you did this test? Orbi? 

[JohnPhotography]

The ethernet is connected as before and iMac still does not recognize it. I've pulled it out and made sure it was fully inserted into the port.

Yes, I'm currently using the iMac wirelessly connected to the Orbi.  

[FURRYe38]

Is it getting an IP address when the LAN cable is connected? Turn OFF the wireless radio on the mac.

Look at the connected clients list on the router, is the mac listed at all here? 

Try different ports on the router same thing? 

[JohnPhotography]

No, not getting a IP address.  iMac is not recognizing the ethernet cable whatsoever.  Yes, I've done the trouble shooting withi wifi turned off.

On the Orbi, i see the iMac connected via wirelessly.  Doesn't even show the iMac being hardwired at all.  Weird.

[FURRYe38]

I would make contact with NG support and ask for help and information on this. Possible you may have a bad router unit. Might ask for an RMA if needed.

@DarrenM